Economic geology and genesis of kaolin resources in the East African Rift system: the case of Alemtena kaolin deposit, Ethiopia

ABSTRACT

The Alemtena kaolin deposit is located within the main Ethiopian rift. New geological, mineralogical, geochemical and physical test data provide evidence of the genesis and potential use of the kaolin. These data indicate that the deposit formed as a result of the intensive weathering of felsic volcanic rocks including rhyolitic tuffs, pumice, and rhyolite. The deposit contains elevated concentrations of Cr + Nb and Ce + Y+La and low concentration of Ba + Sr suggesting the deposit has a supergene origin. The presence of only kaolinite and quartz, and absence of high temperature minerals like pyrophyllite, dickite and pyrite, low bulk density (<2 g/cm³) and high crystallinity (HI > 0.9) strengthen the supergene origin. The presence of comparable grain size distribution, mainly white colour, high Al₂O₃ and kaolinite, relatively low concentrations of Fe₂O₃, TiO₂ and alkali elements make the kaolin favourable for various industrial applications including paper, filler, ceramics, pharmaceuticals, and agricultural industries. Reserve estimation from section logging and pitting gave nearly 85 million tons of reserve.

KEYWORDS:

• Kaolin
• weathering
• Ethiopia
• felsic
• continental rift

Acknowledgements

Addis Ababa University and Geological Survey of Ethiopia provided logistic and financial support for the research. The authors would like to thank Dr. Tetsuichi Takagi of Geological Survey of Japan and Dr. Roy Kuda of AIST for the XRD analysis. We also thank the journal editor, Dr Simon Jowitt and the two anonymous reviewers for the valuable comments and inputs which improved the overall quality of the article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Addis Ababa University; Ministry of Mines and Petroleum.